[TUHS] wump.c for v6
Warner Losh
imp at bsdimp.com
Tue Jan 7 08:14:50 AEST 2020
You have V4 sources? The TUHS archive doesn't have them that I've seen...
Warner
On Mon, Jan 6, 2020, 2:38 PM Clem Cole <clemc at ccc.com> wrote:
> Some day .... So I took a peak at the V5 crt0.s and guess what -- it
> matches!
>
> On Mon, Jan 6, 2020 at 4:08 PM Clem Cole <clemc at ccc.com> wrote:
>
>> You got my curiosity up and found the V5 and V6 source code (I did not
>> have V4 easy to get, where I am today) ;-)
>>
>> A big clue of it being C will be having crt0.s (below) in the first few
>> bytes of the disassembled code. We see the a.out header (i.e. start at
>> offset 20 for the code) and look what's there. I'm going to guess that is
>> at 046 is the address of _main, from the call instruction at address 034.
>> The Trap 1 is a sys exit @ address 044.
>> But .. the V6 crt0.s source has a call to _exit, which is lacking in the
>> binary below. So it means that the binary was not created with the C
>> runtime and probably not the v6 C compiler in the sources. So I took a
>> peak at the V6 crt0.s and guess what -- it matches!
>>
>> So, I'm going to guess the binary was compiled and linked with an earlier
>> compiler. Ao ... if I had to guess, the programs are similar, but possibly
>> different.
>>
>> % more wump.das
>> ;
>> ; pdp11dasm version 0.0.3
>> ; disassembly of wump
>> ;
>> 000000: 000407 br 20 ; ..
>> ;
>> 000002: 005334 dec @(r4)+ ; \.
>> 000004: 004524 jsr r5,(r4)+ ; T.
>> 000006: 002312 bge 37777777634 ; J.
>> 000010: 000000 halt ; ..
>> 000012: 000000 halt ; ..
>> 000014: 000000 halt ; ..
>> ;
>> 000016: 000001 wait ; ..
>> 000020: 170011 setd ; .p
>> 000022: 010600 mov r6,r0 ; ..
>> 000024: 011046 mov (r0),-(r6) ; &.
>> 000026: 005720 tst (r0)+ ; P.
>> 000030: 010066 000002 mov r0,2(r6) ; 6...
>> 000034: 004767 000006 call 46 ; w...
>> 000040: 022626 cmp (r6)+,(r6)+ ; .%
>> 000042: 005000 clr r0 ; ..
>> 000044: 104401 trap 1 ; ..
>> 000046: 004567 005174 jsr r5,5246 ; w.|.
>> 000052: 005746 tst -(r6) ; f.
>> 000054: 012716 011230 mov #11230,(r6) ; N...
>> 000060: 004737 002776 call @#2776 ; _.~.
>> 000064: 004767 002262 call 2352 ; w.2.
>> 000070: 022700 000171 cmp #171,r0 ; @%y.
>> 000074: 001027 bne 154 ; ..
>> 000076: 005004 clr r4 ; ..
>> 000100: 010400 mov r4,r0 ; ..
>> 000102: 006300 asl r0 ; @.
>> 000104: 005760 005334 tst 5334(r0) ; p.\.
>> 000110: 001421 beq 154 ; ..
>> 000112: 032704 000001 bit #1,r4 ; D5..
>> 000116: 001403 beq 126 ; ..
>> 000120: 012716 000024 mov #24,(r6) ; N...
>> 000124: 000402 br 132 ; ..
>> ;
>> 000126: 012716 000003 mov #3,(r6) ; N...
>> 000132: 010400 mov r4,r0 ; ..
>> 000134: 006300 asl r0 ; @.
>> 000136: 016046 005334 mov 5334(r0),-(r6) ; &.\.
>> 000142: 004737 002776 call @#2776 ; _.~.
>>
>>
>>
>>
>>
>> V6: s4/crt0.s:
>> / C runtime startoff
>>
>> .globl savr5
>> .globl _exit
>>
>> .globl _main
>>
>> start:
>> setd
>> mov sp,r0
>> mov (r0),-(sp)
>> tst (r0)+
>> mov r0,2(sp)
>> jsr pc,_main
>> mov r0,(sp)
>> jsr pc,*$_exit
>> sys exit
>>
>> .bss
>> savr5: .=.+2
>>
>> V5: s4/crt0.s:
>> / C runtime startoff
>>
>> .globl savr5
>>
>> .globl _main
>>
>> start:
>> setd
>> mov sp,r0
>> mov (r0),-(sp)
>> tst (r0)+
>> mov r0,2(sp)
>> jsr pc,_main
>> cmp (sp)+,(sp)+
>> clr r0
>> sys exit
>>
>> .bss
>> savr5: .=.+2
>>
>> On Mon, Jan 6, 2020 at 1:48 PM Warner Losh <imp at bsdimp.com> wrote:
>>
>>>
>>>
>>> On Mon, Jan 6, 2020 at 11:38 AM Will Senn <will.senn at gmail.com> wrote:
>>>
>>>> On 1/6/20 12:29 PM, Warner Losh wrote:
>>>>
>>>> The good news is that disassembly will tell you right away if it was
>>>> written in C or not.
>>>>
>>>>
>>>> OK. I give up. How?
>>>>
>>>
>>> Generally, the C compiler generates code that's quite distinctive (at
>>> least PCC does, not sure about Dennis' compiler). People writing free
>>> assembler tend to do really weird things for function entry / return.
>>>
>>> And it will likely tell you if it's some weird wrapper around another
>>> binary, though that wasn't too common at bell labs.
>>>
>>> Warner
>>>
>>
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